AN independent Scotland would not be able to join Nato unless it formally
accepted its “nuclear umbrella”, according to the organisation’s former
secretary general.

Lord Robertson of Port Ellen, who as George Robertson was a Labour defence secretary, said the confirmation from Nato that a separate Scottish state would have to apply for membership had left the SNP facing a “huge dilemma”.

It is committed to getting rid of Trident on the Clyde and he questioned whether its rank and file members would swallow the requirement to recognise the “supremacy” of US, UK and French nuclear weapons.

Opposition parties said Nato’s statement had left Alex Salmond’s defence policy in a “total mess”.

Lord Robertson supervised the entry of seven new members of Nato in 2002 and each one had to accept its strategic concept stating that “as long as nuclear weapons exist, Nato will remain a nuclear alliance”.

He said: “Either the SNP accept the central nuclear role of Nato and show that they will shed any principle to buy votes for separatism, or they reject the nuclear role of Nato and ensure that a separate Scottish state stays out of the world's most successful defence alliance."

The former cabinet minister added that all members of Nato, including Norway and Canada, backed the statement in favour of a nuclear deterrent.

He asked: “Does the SNP accept this unambiguous acceptance of the nuclear umbrella? The Strategic Concept has other deep problems for an SNP government. It goes on to say this: ‘The supreme guarantee of the security of the Allies is provided by the strategic nuclear forces of the Alliance, particularly of the United States; the independent strategic nuclear forces of the United Kingdom and France, which have a deterrent role of their own, contribute to the overall deterrence and security of the Allies”.

“Can the SNP, and its rank and file membership, swallow this unavoidable obligation? And where does the immediate expulsion of the Trident fleet from Scotland fit in this condition?”

He stepped into the debate after Nato said it had not had any discussions on Scottish independence, but a new state would not be a party to the North Atlantic Treaty, and therefore not a member of the alliance.

Michael Moore, the Scottish Secretary, said the First Minister had finally been forced to accept what everyone else has been telling him, that an independent Scotland would need to apply to Nato.

He added: “The SNP's party policy on Nato passed last year specifically states that, 'On independence, Scotland will inherit its treaty obligations with Nato'. This is a major u-turn by the party on their Nato policy and it shows that their claims have no foundation.”

Responding to a question from BBC Scotland, Nato said: "It appears widely agreed that, as a matter of law, a Scotland which has declared its independence and thereby established its separate statehood would be viewed as a new state.

"In the Nato context, the definitive determination on this question would be made by the member states, acting in the North Atlantic Council. If it were to choose to apply for Nato membership, its application would be subject to the normal procedure, as outlined in Article 10 of the Treaty."

The SNP is committed to non-nuclear membership of Nato after performing a controversial about turn on its previous opposition to the organisation at its annual conference last year.

Mr Salmond, who is in the US for the Scotland Week celebrations, said he was “certain” that its members would accept an independent Scotland opposed to nuclear weapons.

The First Minister, who has repeatedly pointed out that 25 of the 28 Nato members are non-nuclear, said membership could be negotiated in the period between a "yes" vote and Scotland becoming independent.

He added: “You have to come to agreement with your colleagues, and in that sense there is a parallel with the European Union, you notify your intent to remain a member.

"It is the exception rather than the rule to be a nuclear country, only Britain, France and America possess nuclear weapons.

"Many members of Nato, like Canada and Norway, have made it clear they won't host nuclear weapons on their soil, and that is respected by the other partners in the alliance.”

Jim Murphy, the Labour shadow defence secretary, said the SNP’s defence policy was in a “total mess”, adding: “This is yet another fact that the SNP wanted to keep Scotland in the dark about."

Ruth Davidson, the Scottish Conservative leader, said the SNP’s “chaotic” approach to Nato was to “stick its fingers in its ears and hope the assertions repeatedly made will eventually come true".